Important insights into the mechanisms of human carcinogenesis have come from the study of DNA tumor viruses. The DNA tumor virus adenovirus provides an ideal system for investigating transcriptional events in cellular transformation. The long-term goal of our research is to understnd the mechanism by which the adenovirus E1A protein alters the normal cellular transcriptional program so as to induce transformation. Here, we focus on the transcriptional regulation of the cellular c-fos gene by the adenovirus 243R E1A protein, and the functional interaction between E1A and the cellular transcriptional machinery. Our previous studies have identified a link between the action of E1A and an important intracellular signling system, the cAMP-dependent protein kinase pathway. This interaction results in the activation of a set of genes that are involved in cellular growth control and transformation. Knowledge gained from studying the effects ofE1A on cellular transcriptional regulation wil lead to better understanding of the molecular events involved in transformation. 1) Identifiction transacting factors involved in the activation of c-fos by E1A and cAMP, A 22 nucleotide "E1A-response element" (ERE) has been identified that mediates activation of c-fos by the 243R E1A protein. The ERE contains binding sites for transcription factors ATF/CREB and YY1. Factors tht bind the ERE will be identified, and the effects of E1A and cAMP on their level and activity will be determined. 2) Structure and function of the ATF/CREB-YY1 complex. YY1 physically interacts with members of the AFT/CREB family of transcription factors. As a prelude to investigating the role of the ATF/CREB-YY1 complex in activation b E1A, structure/function analysis of the ATF/CREB-YY1 interaction will be performed. DNA-binding and transcriptional repression by the complex will also be investigated. 3) The ATF/CREB-YY1 complex as a target ofE1A. E1A can bind to YY1 and alter its DNA-binding properties. The interaction between E1A and YY1, and between E1A and the ATF/CREB-YY1 complex will e studied. Experiments will include structure/function analysis of the E1A-YY1 interaction, as well as in itro and in vivo binding assays. These experiments will lead to a model for the molecular basis of E1a activation of thec-fos gene.